Dimensionality Control of Electronic Phase Transitions in Nickel-Oxide Superlattices

TL;DR

This study demonstrates that by fabricating LaNiO3/LaAlO3 superlattices with atomic precision, one can control the dimensionality of the electron system, inducing metal-insulator and magnetic transitions in ultra-thin layers.

Contribution

The paper introduces a method to precisely control the dimensionality of correlated-electron systems using atomically engineered superlattices, revealing tunable quantum phase transitions.

Findings

Superlattices with LaNiO3 layers as thin as two unit cells undergo phase transitions.

Thicker LaNiO3 layers remain metallic and paramagnetic at all temperatures.

Dimensionality control enables tuning of collective electronic phases.

Abstract

The competition between collective quantum phases in materials with strongly correlated electrons depends sensitively on the dimensionality of the electron system, which is difficult to control by standard solid-state chemistry. We have fabricated superlattices of the paramagnetic metal LaNiO3 and the wide-gap insulator LaAlO3 with atomically precise layer sequences. Using optical ellipsometry and low-energy muon spin rotation, superlattices with LaNiO3 as thin as two unit cells are shown to undergo a sequence of collective metalinsulator and antiferromagnetic transitions as a function of decreasing temperature, whereas samples with thicker LaNiO3 layers remain metallic and paramagnetic at all temperatures. Metal-oxide superlattices thus allow control of the dimensionality and collective phase behavior of correlated-electron systems.